Narrow skulls clue to first Americans

Narrow skulls clue to first Americans
11:24 04 September 03
NewScientist.com news service
Jeff Hecht

Skull measurements on the remains of an isolated group of people who
lived at the southern tip of Mexico's Baja California has stirred up
the debate on the identity of the first Americans once again.

The earliest inhabitants of North America differed subtly but
significantly from modern native Americans. The difference is clearly
seen in the skull shapes of the first people to colonise the
continent, who had longer, narrower skulls than modern people.

One theory says it is because two distinct groups of people migrated
to North America at different times. But another theory says that
just one population reached the continent and then evolved different
physical attributes, except for a few isolated groups.

Anthropologists once assumed the earliest Americans resembled modern
native Americans. That changed with the discovery of a 10,500-year-
old skeleton called Luzia in Brazil, and the 9000-year-old skeleton
of Kennewick man in Washington state.

Both had the long, narrow skulls that more resemble those of modern
Australians and Africans than modern native Americans, or even the
people living in northern Asia, who are thought to be native
Americans' closest relatives.

Some researchers argued that they were simply unusual individuals,
but scientists have now identified the same features in recent
remains from the Baja California.

Desert island

The Pericú hunter-gatherers survived until just a few hundred years
ago at the end of the peninsula, says Rolando González-José, of the
University of Barcelona, Spain, (Nature, vol 425, p 62).

He thinks the formation of the Sonora desert isolated the Pericú for
thousands of years, but they vanished when Europeans disrupted their
culture. González-José measured 33 Pericú skulls and found their
features were similar to those of the ancient Brazilian skulls.

This backs the idea that a first wave of long, narrow skulled people
from south-east Asia colonised the Americas about 14,000 years ago.
These were followed by a second wave of people from north-east Asia
about 11,000 years ago, who had short skulls.

This theory has been championed by Walter Neves, at the University of
Sao Paulo, Brazil. He says the second wave may have been larger, and
eventually came to dominate the Americas. "The discovery is exactly
what I have been predicting since the late 1980s," Neves told New
Scientist.

However Joseph Powell, an anthropologist at the University of New
Mexico in Albuquerque, is not convinced. He thinks the earliest
Americans did come from south-east Asia, but believes they evolved
into modern native Americans.

"Even with two waves, each would have changed over the past 10,000 to
12,000 years through adaptation and microevolution," he says. Neves
argues that the change in skull shape after 8000 years ago is too
sudden for evolution.

Journal reference: Nature (vol 425, p 62)